It has been known to produce an epitaxial silicon wafer by vapor phase growth of an epitaxial film on a surface of a silicon wafer obtained by cutting a monocrystal silicon.
When the epitaxial film of the epitaxial silicon wafer is contaminated with metal impurities, semiconductor device performance is deteriorated. Hence, studies have been made in order to remove the contamination on an epitaxial film caused by metal impurities (see, for instance, Patent Literature 1: JP-A-11-243093).
Patent Literature 1 discloses a method for obtaining a semiconductor device, in which the contamination caused by nickel (metal impurities) is removed. Specifically, Patent Literature 1 discloses: growing an epitaxial film on a surface of a low-resistance silicon wafer (p+ silicon wafer) containing boron; and cooling the epitaxial silicon wafer in a temperature range (from 900 degrees C. to 700 degrees C.) at a cooling rate of 40 degrees C./min or less, thereby obtaining an epitaxial silicon wafer whose oxygen precipitation density is in an order of 105 to 107/cm2.
The epitaxial silicon wafer having the above oxygen precipitation density is thermally treated in a manufacturing process of the semiconductor device, whereby nickel in the epitaxial film is removed by intrinsic gettering and an epitaxial silicon wafer from which the contamination caused by nickel is removed can be obtained.
In recent years, the heat treatment temperature in the manufacturing process of semiconductor device has come to be reduced to, for instance, less than 900 degrees C. When the heat treatment temperature is thus reduced, it is possible that nickel in the epitaxial silicon wafer obtained by the method disclosed in Patent Literature 1 is not sufficiently removed by intrinsic gettering.